NIT
( 150 )
N I T
ioo parts
Pale nitric acidBright yellow acidOrange colouredDark green - -
Azot
Oxygen.
the
ion
I
2.389
J £ S \
I
2 -344
V i« 0 1
I
2.292
Us J
I
2,230
The quantities of true nitric acid (or thatproduced in the aeriform hate by faturatingnitrous gas with oxygen) in folutions of differ-ent denfities is thus given, being inferred frommixtures of the ftandard liquid acid with knownweights of water.
100 parts ofNitric Acid of fp. gr.
True
Acid.
Water.
I.5040
1-4475
1.4285
i-39° 6
i-355i
1.3186
1.3042
1.2831
1.2090
.5
>Ii
0
9 1 -5580.39
7 i -<55
62.96
56.88
5 2 -°3
49.04
46.03
•45-27
8-45
19.61
2 8.35
37.04
43-12
47-97
50.96
53- 97
54- 73
The dilute, nitric acids undergo fimilarchanges by nitrous gas as the concentrated, butthe quantity of gas which the acid is capableof abforbing diminifhes in proportion to thedegree of dilution. Mr. D. found that 330grs. of acid of 1.36 fp. gr. became blue greenafter 50 cubic inches of gas had been pafiedthrough it, and the fpecific gravity was leflenedto 1-351. It had gained in weight but 3 grainsand when heated only 7 cubic inches of nitrousgas were colle&ed.
There is a difficulty in accounting for all thechanges of fpecific gravity in the experimentsabove mentioned. Nitric acid undoubtedlylofes fpecific gravity by abforbing nitrous gas,and by a direift experiment a pale acid of 1.504was reduced to 1 *474 by compleat figuration■with the gas. And on the other hand the fame.jicid of 1.474 after being heated and brought to-the ft ate of the pale nitric returned to thefpecific gravity of 1.502 or nearly to its originalweight. But on the other hand the yellow acidof 1.5 lojl fpecific gravity by lofing nitrous gasand was reduced to 1.491. Probably thisapparent contradiction depends upon the vari-
* triHi Tranf. vol
able quantity of nitric acid united with thenitrous gas in the form of nitrous vapour, inwhich it always exifts when expelled from thecoloured acids.
Mr. Kirwan in his excellent experiments onthe ftrength of acids purfues the followingmethod in eflimating the quantity of real acidin folutions of nitric acid of different denfities.
The fpecific gravity of the moft concentratednitrous acid which he could produce was 1.5543in the temperature of 6o°. This was highlyfuming and yellow, and therefore confiftecl ofnitric acid holding nitrous gas in folution.This laft circumftance however is neglected.He confiders this as,the Jlandardacid: and by cal-culations which will be given in the appendixhe deduces the proportions of ftandard in 100parts of diluter acids whofe fpecific gravity isgiven. Thus for example, 100 parts of an acidof 1.4731 Ip- g r - are found by calculation tocontain 90 parts of the ftandard acid of 1.5543and 10 parts of water. But the ftandard itfeifis a mixture of water with an unknown quantityof real acid, and to determine this quantity Mr.Kirwan purfues the following method which isapplied (mutaiis mutandis ) to the other acids. 1Firft, a known quantity of alkali is faturatedwith an acid whofe fpecific gravity is known,and whofe proportion of ftandard acid is deter-mined by previous calculation. Then anotherfolution is made of a known quantity of thefame neutral fait as that produced by the unionof the acid and alkali employed, and both folu-tions are brought to the fame fpecific gravity byadding water to the heavieft. This gives twofolutions which may be prefumed to hold equalquantities of neutral fait, and the quantity ofready-formed fait in one of the folutions i*known by a£tual experiment, and the quantityof alkali and ftandard acid required to makethis quantity of neutral fait in the other folutionis alfo known by experiment. From thefe datathe quantity of real acid in the ftandard maybe readily inferred, underftanding by the termreal acid an acid of the degree of concentrationthat exifts in the dry neutral fait combined withthe alkali, An example will render this clearer
. iv.p. 1 7 and 35,
\